2002 quad with 4.7 started hearing a snapping noise from under the hood. With everything off in truck you hear it driving down the road. Louder when accelerating. I’m thinking it is a bad coil causing a misfire. How can I confirm this? I know all plugs should be replaced due to high mileage on them but can I just replace the faulting one and coil until weather permits changing all?

How owe do I figure out the bad one?